trace.h Example File

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 #ifndef TRACE_H
 #define TRACE_H

 #include <QtCore/QDebug>

 #define ENABLE_TRACE
 //#define VERBOSE_TRACE

 namespace Trace {

 class NullDebug
 {
 public:
     template <typename T>
     NullDebug& operator<<(const T&) { return *this; }
 };

 inline NullDebug nullDebug() { return NullDebug(); }

 template <typename T>
 struct PtrWrapper
 {
     PtrWrapper(const T *ptr) : m_ptr(ptr) { }
     const T *const m_ptr;
 };

 } // namespace Trace

 template <typename T>
 inline QDebug& operator<<(QDebug &debug, const Trace::PtrWrapper<T> &wrapper)
 {
     QDebugStateSaver saver(debug);
     debug.nospace() << '[' << static_cast<const void *>(wrapper.m_ptr) << ']';
     return debug;
 }

 template<typename T>
 inline const void *qtVoidPtr(const T *ptr)
 { return static_cast<const void *>(ptr); }

 #define qtThisPtr() qtVoidPtr(this)

 #ifdef ENABLE_TRACE
         inline QDebug qtTrace() { return qDebug() << "[qmlvideo]"; }
 #    ifdef VERBOSE_TRACE
         inline QDebug qtVerboseTrace() { return qtTrace(); }
 #    else
         inline Trace::NullDebug qtVerboseTrace() { return Trace::nullDebug(); }
 #    endif
 #else
     inline Trace::NullDebug qtTrace() { return Trace::nullDebug(); }
     inline Trace::NullDebug qtVerboseTrace() { return Trace::nullDebug(); }
 #endif

 #endif // TRACE_H